Lysostaphin, a metalloendopeptidase that is bacteriolytic for Staphylococcus aureus, is a potential systemic therapy for treating multidrug-resistant S. aureus mediated infections. However, the short half life of this enzyme in vivo has precluded its development thus far as a systemic therapy. Our company, PharmaIN proposes to apply a novel drug delivery nanotechnology (drug nanocarrier) called Protected Graft Copolymers (PGC) coupled with PharmaIN's Reversible Binding (PRB), a new technology for the reversible formulation of peptides and/or proteins containing a metal binding site to the drug nanocarrier. Importantly, the fact that the nanocarrier concentrates at sites of increased vascular permeability affords the ability to concentrate associated agents at the site of infection. Our long-term goal is to develop this delivery system for lysostaphin that, considering its Zn-binding domain, appears to be particularly well suited for association with our carrier. The envisioned formulation would not only offer the ability to prolong the circulation time of the enzyme but also concentrate the agent at sites of infection, potentially increasing efficacy, decreasing overall dose over the entire treatment period and suppressing the emergence of resistance. In the Phase I project, we propose the following: Aim 1: Design, synthesis, purification and characterization of PGC with PRB. Aim 2: Formulation of lysostaphin with PGC/PRB and determination of (i) formation efficiency of PGC/PRB:lysostaphin complex, (ii) dissociation constant of lysostaphin from the PGC/PRB in the presence and absence of serum, (iii) the ability, in vitro, to release lysostaphin from carrier in the presence of imidazole and substrate and maintain its activity without denaturation. Aim 3: Comparison of in vivo pharmacokinetic parameters of PGC/PRB:lysostaphin complex and lysostaphin. The Phase II studies will involve a comprehensive evaluation of formulated lysostaphin including biodistribution (accumulation at sites of infection) and efficacy in an animal model of staphylococcal infection. The studies are aimed toward filing an IND for the envisioned product - lysostaphin in an optimal infection site-directed delivery system for the treatment of invasive staphylococcal infections. Public Health Relevance: The available therapies for antibiotic resistant S. aureus bacteria are limited and the emergence of numerous high-level vancomycin resistant bacteria predicts a dire public health situation if new treatments aren't developed. This Phase I application is aimed toward developing a life-saving product for use in life threatening emergency caused by invasive and systemic staphylococcal infections with the eventual goal of FDA filing of an IND application. The product will contain an enzyme (lysostaphin) to digest bacterial cell walls and a nanocarrier drug delivery system that would make the enzyme stable to clear infections in blood and tissue of the patients.